特别是在dotnet核心2.2中，你必须改变SignalR

.WithOrigins (http://localhost: 3000)或

.SetIsOriginAllowed(isOriginAllowed: _ => true) //所有源

用.AllowCredentials()代替。allowanyorigin ()

https://trailheadtechnology.com/breaking-change-in-aspnetcore-2-2-for-signalr-and-cors/

https://github.com/aspnet/AspNetCore/issues/4483

适用于。net Core 1和。net Core 2

如果使用.Net-Core 1.1

不幸的是，在这个特定的情况下，文件非常混乱。所以我要让它变得非常简单:

将Microsoft.AspNetCore.Cors nuget包添加到项目中 在ConfigureServices方法中添加services.AddCors(); 在Configure方法中，在调用app.UseMvc()和app.UseStaticFiles()之前，添加: app.UseCors(生成器=>生成器 .AllowAnyOrigin () .AllowAnyMethod () .AllowAnyHeader () .AllowCredentials ());

就是这样。每个客户端都可以访问您的ASP。NET核心网站/API。

如果使用。net - core 2.0

Add Microsoft.AspNetCore.Cors nuget package to your project in ConfigureServices method, before calling services.AddMvc(), add: services.AddCors(options => { options.AddPolicy("AllowAll", builder => { builder .AllowAnyOrigin() .AllowAnyMethod() .AllowAnyHeader() .AllowCredentials(); }); }); (Important) In Configure method, before calling app.UseMvc(), add app.UseCors("AllowAll"); "AllowAll" is the policy name which we need to mention in app.UseCors. It could be any name.

得到这个工作与。net Core 3.1如下:

在ConfigureServices()方法中:

 public void ConfigureServices(IServiceCollection services)
  {
   ...
   services.AddCors();
   ...
  }

在Configure()方法中:

 public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
  {
   ...
   app.UseCors(builder =>
          builder.AllowAnyOrigin()
          .AllowAnyHeader()
          .AllowAnyMethod()
        );
   ...
  }

你必须在Startup.cs类中进行配置

services.AddCors(options =>
        {
            options.AddPolicy("CorsPolicy",
                builder => builder.AllowAnyOrigin()
                .AllowAnyMethod()
                .AllowAnyHeader()
                .AllowCredentials());
        });

ASP。NET Core 6:

var  MyAllowSpecificOrigins = "_myAllowSpecificOrigins";

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddCors(options =>
{
    options.AddPolicy(name: MyAllowSpecificOrigins,
                      builder =>
                      {
                          builder.WithOrigins("http://example.com",
                                              "http://www.contoso.com");
                      });
});

// services.AddResponseCaching();

builder.Services.AddControllers();

var app = builder.Build();
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();

app.UseCors(MyAllowSpecificOrigins);

app.UseAuthorization();

app.MapControllers();

app.Run();

更多样品请参考官方文档。

ASP。NET Core 3.1和5.0:

你必须在应用程序启动时在ConfigureServices方法中配置CORS策略:

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(o => o.AddPolicy("MyPolicy", builder =>
    {
        builder.WithOrigins("http://example.com")
               .AllowAnyMethod()
               .AllowAnyHeader();
    }));

    // ...
}

builder中的CorsPolicyBuilder允许您根据需要配置策略。你现在可以使用这个名字将策略应用到控制器和动作上:

[EnableCors("MyPolicy")]

或者把它应用到每一个请求上:

public void Configure(IApplicationBuilder app)
{
    app.UseCors("MyPolicy");

    // ...

    // This should always be called last to ensure that
    // middleware is registered in the correct order.
    app.UseMvc();
}

这涵盖每个端点。如果你想阻止某个端点，使用这个注释[DisableCors] 这里描述得很好。 https://learn.microsoft.com/en-us/aspnet/core/security/cors?view=aspnetcore-5.0

在app.authentication()和app.routing()之间添加app.usecors(policyName)在Configure方法中。 在configureService方法中

services.AddCors(options => options.AddPolicy(name: mypolicy,     builder =>     { builder.AllowAnyHeader().AllowAnyMethod().AllowAnyOrigin(); }));

在每个控制器中添加[EnableCors("mypolicy")]

        [EnableCors("mypolicy")] 
        [Route("api/[controller]")] [ApiController] 
        public class MyController : ControllerBase

eg:-

  namespace CompanyApi2
        {
            public class Startup
            {
                public Startup(IConfiguration configuration)
                {
                    Configuration = configuration;
                }
        
                public IConfiguration Configuration { get; }
        
                // This method gets called by the runtime. Use this //method to add services to the container.
                public void ConfigureServices(IServiceCollection services)
                {
                    services.AddCors(options =>
                        options.AddPolicy(name: mypolicy,
                            builder =>
                            {
                                builder.AllowAnyHeader().AllowAnyMethod()
                                    .AllowAnyOrigin();
                            })); //add this
                    services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
                    services.AddScoped<IDatarepository, DatabaseRepository>();
                }
        
                public string mypolicy = "mypolicy";
        
                // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
                public void Configure(IApplicationBuilder app, IHostingEnvironment env)
                {
                    if (env.IsDevelopment())
                    {
                        app.UseDeveloperExceptionPage();
                    }
                    else
                    {
                        app.UseHsts();
                    }
        
                    app.UseCors(mypolicy); //add this
                    app.UseHttpsRedirection();
                    app.UseMvc();
                }
            }
        }